Magnet system for focusing the electron beam in a high-power klystron

ABSTRACT

A SYSTEM FOR PROVIDING A SPATIAL PERIODIC MAGNETIC FIELD FOR FOCUSING THE ELECTRON BEAM OF A HIGH-POWER KLYSTRON BY ARRANGING A NUMBER OF ANNULAR MAGNETIC RINGS HAVING AXIAL MAGNETIZATION IN THE SAME SENSE COAXIALLY AROUND THE DRIFT TUBES BETWEEN RESONANT CAVITIES.

United States Patent Inventors Vladimir Dubravec ReIlingen; Kurt Hirsch, Hamburg, Germany App]. No. 855,803 Filed Sept. 8, 1969 Patented June 28, 1971 Assignee U.S. Philips Corporation New York, NY.

Priority Sept. 7, 1968 Germany P17910804 MAGNET SYSTEM FOR F OCUSING THE ELECTRON BEAM IN A HIGH-POWER KLYSTRON 6 Claims, 2 Drawing Figs.

US. Cl 3l5/5.35, 335/210 Int. Cl H01j 23/08 [50] Field of Search [56] References Cited UNITED STATES PATENTS 2,741,718 4/1956 Wang 3l5/5.34X 3,259,788 7/1966 Orui 315/3.5 3,271,616 9/1966 Verger 315/35 3,394,282 7/1968 Schmidt 315/535 Primary ExaminerI-Ierman Karl Saalbach Assistant Examiner-Saxfield Chatmon, .Ir. ArtorneyFrank R. Trifari ABSTRACT: A system for providing a spatial periodic magnetic field for focusing the electron beam of a high-power klystron by arranging a number of annular magnetic rings having axial magnetization in the same sense coaxially around the drift tubes between resonant cavities.

PATENTEnJunzslsn 3,588,582

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INVENTORS VLADIMIR OUBRAVEC BY KURT HIRSCH AGENT MAGNET SYSTEM FOR FOCUSING THE ELECTRON BEAM IN A HIGH-POWER KLYSTRON The invention relates to a magnet system for focusing the electron beam in a high-power klystron, in which a spatial periodic magnetic field is generated by means of permanent magnets which are arranged in the spaces between the resonant cavities and are all magnetized axially in the same sense.

Such an arrangement is known from German Patent Specification 1,l58,183. The permanent magnets each consist of a restricted number of columns, usually not more than two, built up from fiat magnetic discs. The columns adjoin soft magnetic yokes which in turn are formed into pole shoes near the drift tubes of the klystron.

The drawbacks of the known arrangement on the one hand is that the generated fields are not sufficiently circular-symmetrical which can hardly be corrected with extra soft-magnetic material. On the other hand, the weight of such a magnet system is so high that it is not attractive to deliver each tube with an individual magnet system adjusted in the factory.

It is the object of the invention to mitigate or avoid the above-mentioned drawbacks.

According to the invention, in a magnet system for focusing the electron beam in a high-power klystron in which a spatial periodic magnetic field is generated by means of permanent magnets which are arranged in the spaces between the resonant cavities and are all magnetized axially in the same sense, the permanent magnets each consist of at least three rings which surround the drift tubes of the klystron coaxially and with some intermediate space, the rings of one magnet showing mutual distances. The inside diameter of the magnetic rings preferably is at most twice the outside diameter of the drift tubes. 1

The arrangement according to the invention first of all has the advantage that the weight is considerably smaller than in the known constructions. The leakage field also is smaller which involves the possibility of a more complex construction of the transmitter. The low weight enables the combination in the factory of each tube with its own magnets. In connection with the assembly the rings are divided into two equal segments. l

As a result of the fact that each magnet consists of at least three rings, the field inside the magnet but also between two magnets, namely. within a resonant cavity, can easily be adjusted. For reasons of symmetry each magnet preferably consists of at least four rings.

According to the invention, the outermost magnetic rings can be provided with magnetic discs which end in pole shoes which may penetrate into the readily conducting wall of the drift tubes. 7

By providing soft-magnetic discs which may be movable mutually, between the rings, both axial adjusting possibilities are available and corrections of inhomogeneities of the magnets owing to eccentric displacement of said discs. An electron beam which is fired at an angle or a small curvature in the tube can also be corrected herewith. The soft-magnetic discs, if desirable in cooperation with other nonmagnetic or diamagnetic discs, may contribute to the cooling.

It is to be noted that the use of a number of rings magnetized in the same sense is known in travelling wave tubes. In this case the rings adjoin each other without intermediate space or with soft-magnetic intermediate members. In this case no periodic field is generated.

It is also known to generate a spatial periodic field by means of magnets which each consist of two rings magnetized axially in the same sense. However, as a result of the small number or rings the construction is not suitable for large intermediate spaces between the individual magnets as is required in highpower klystrons.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying drawing, in which:

FIG. 1 shows an arrangement according to the principle of the invention; and

IG. 2 is a graph showing the magnetic field which is obtained with the arrangement shown in FIG. 1.

Referring now to FIG. 1, two drift tubes of a klystron are denoted by 1 and 2, respectively. An electron beam moves in the direction of the arrow 3. The interaction gaps are denoted by 4. Resonant cavities which are not shown to avoid complexity of the drawing adjoin said interaction gaps. Four axially magnetized permanent magnetic rings 5 are arranged around each of the drift tubes and produce a field 6 of an intensity I-I within the drift tubes and a field 7 of intensity H in the interaction gaps. The intermediate spaces between the rings 5 are denoted by 9. The outermost rings have pole shoes 8. The intermediate rings and the inner surfaces of the outermost rings are covered with soft-magnetic discs 10 between which soft-magnetic discs 10 adjoin which are shown only at one intermediate space The discs 10 are radially movable. The permanent magnetic rings and the soft-magnetic discs each consist of two equal segments for reasons of assembling. The connection means are not shown.

In FIG. 2 the curve 17 denotes the magnetic field within the drift tube 1 and the curve 18 the field within the drift tube 2. In the space between the two magnets the field has the variation 19, 20. The depth of the saddle in 17 and 18 can be adjusted by moving the inner rings towards or away from the outermost rings. This is shown in broken lines in FIG. 2. The depth of this saddle in 17 and I8 is preferably made equal to that of the saddle in 19, 20.

In a given case for the known construction of a four-cavity klystron of 20 kw. output power the weight of the magnet system was kgms. with a peak value of the field of 400 Oerstedt. In a construction according to the invention this weight was 20 kgms.

We claim:

1. A magnet system for focusing an electron beam in a highpower klystron having drift tubes between resonant cavities comprising at least three-spaced permanent magnetic rings coaxially arranged around each drift tube to produce a spatial periodic magnetic field within each tubes, said rings being magnetized axially in the same sense.

2. A magnet system as claimed in claim 1 wherein the inside diameter of the magnetic rings does not exceed twice the outside diameter of the drift tube.

3. A magnet system as claimed in claim 1 having four magnetic rings between resonant cavities.

4. A magnet system as claimed in claim 1 further including means to axially move at least one of the magnetic rings relative to another to vary characteristics of the special periodic magnetic field within each drift tube.

5. A magnet system as claimed in claim 1, further including soft magnetic discs abutting the magnetic rings and means to radially move said soft magnetic discs for correcting inhomogeneities in the spatial periodic magnetic field within each drift tube.

6. A magnet system as claimed in claim 5 wherein the permanent magnetic rings and the soft-magnetic discs each comprise two equal segments.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,588,582 Dated June 28, 1971 In n fl VLADIMIR DIJBRAVEC AND KURT HIRSCH It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 1, change or to -of line 23, change "10" to --llline 39, before "field insert --magnetic- Signed and sealed this 2nd day of November 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOITSCHALK Acting Commissioner of Patents Attesting Officer 

